DE2239549A1 - OVER-TEMPERATURE DISPLAY AND PROTECTION DEVICE, ESPECIALLY IN CATALYTIC EMISSION CONTROL SYSTEMS OF COMBUSTION MACHINERY - Google Patents

Description

Patent application August 4, 1972

Applicant: ADAM OPEL AKTIENGESELLSCHAFT, RUSSELSHEIM / HESSEN

Device to protect against overheating or to display the temperature in exhaust gas decontamination systems of internal combustion engines, primarily in motor vehicles

The invention relates to a device for protecting against overheating or for displaying the temperature in exhaust gas decontamination systems, in particular catalytic converters or reactors, of internal combustion engines, primarily in Motor vehicles.

With catalytic converters for the detoxification of car exhaust fumes it is of the utmost importance for the functionality of the converter that it is not overheated, for example can happen due to the failure of a spark plug. Accordingly, such systems require a reliable one Temperature display to avoid the risk of incurable damage to the converter due to overheating in good time to recognize and avert.

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The object of the present invention is to provide such To create display and protection device that is simple and reliable in its mode of operation is. This goal is achieved according to the basic idea of the invention in that a with in the exhaust gas decontamination system constant current strength electrically heated wire is arranged, which when elongated as a result of heating by opening Contacts automatically interrupts the heating circuit and automatically closes it again after cooling and that the The cooling times of the heating wire depending on the respective temperature in the exhaust gas decontamination system as an initial measure for determining and displaying the temperature in the exhaust gas decontamination system and / or as a signal for switching on serve as a warning display and / or to switch off the exhaust gas decontamination systems.

Because of the current, this wire lengthens. After reaching a certain temperature and a corresponding one Elongation, the power supply is interrupted. Depending on the temperature difference between the jumper wire and the the exhaust gas decontamination system surrounding it, the cooling time of the wire, i. H. the time until it contracted to a length at which the contact for the power supply to a heater closes again, different To be long. It is obvious that when the cooling times exceed a certain time value, that is

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the switch-off time is correspondingly long, the temperature of the converter must have increased, since then the cooling process is no longer as intense as before. Which is made up of The rectangular curve of the heating current resulting from switching the circuit on and off can be achieved by means of an integrator converted into a steady stream. The level of this constant current leaving the integrator can can be used to display a warning or to operate an actuator to prevent damage caused by overheating.

Another feature of the invention, which is particularly useful for a catalytic converter as an exhaust gas decontamination system is suitable, is characterized in that the heating wire is stored and guided in a sleeve that is on all sides is enclosed by the converter mass. On the one hand, this results in an optimal heat transfer from the converter material the heating wire guaranteed. On the other hand, this can be unhindered by the converter material surrounding it perform axial displacements due to changes in length.

In order to keep the heating energy for the heating wire low (low heating current consumption), it is advisable to use the heating wire to train as long as possible. Optimal results can be achieved according to a related proposal of the invention achieve that the sleeve and hot wire length at least correspond to the entire width of the catalytic converter.

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According to a further feature of the invention, the heating wire is firmly connected at one end to one end of the sleeve and the other end of the heating wire protrudes from the associated open sleeve end and forms one contact for actuation of the heating circuit.

The sleeve surrounding and guiding the heating wire is expediently made of a material with a coefficient of thermal expansion that is comparatively low compared to the heating wire. As a sleeve material, for example, ceramic material or glass - provided these substances withstand vehicle vibrations. Good test results could also be achieved by making the sleeve from a steel with about 36 % nickel and the heating wire from steel X 15Cr Ni Si 2520. The first-mentioned material has a coefficient of thermal expansion of approximately

0.9 · 10 o ^to »while the coefficient of thermal expansion for the latter material amounts to about 19 · 10.

If a ceramic or glass sleeve is used, the hole can be due to the low thermal expansion and -Conductivity of this material can be adapted approximately to the diameter of the heating wire, so that optimal guidance the same is possible without further aids. When using a steel sleeve, on the other hand, it is advisable to

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The diameter of the bore should be chosen to be significantly larger than that of the heating wire. In order to ensure perfect management of the same here as well to ensure, it is proposed according to a further feature of the invention that the heating wire within the sleeve is guided at individual points by means of cemented ceramic sleeves.

As a switch housing, d. H. to accommodate the at the free end of the heating wire located contact and with this cooperating mating contact, the invention proposes that To use closure piece with which the filling opening of the converter is closed and sealed at the same time. For this purpose, the closure piece is to be designed to be hollow and to be welded or cemented to the sleeve. Through the The design of the temperature sensor described at the same time as a converter sealing plug is advantageously a simple one Installation and replacement of the sensor possible.

Since not only the heating wire, but also the sleeve is subject to certain changes in length due to thermal expansion, is further proposed that the closed end of the sleeve facing away from the closure piece in one with the converter housing connected bearing is held or guided so that it can move axially.

To prevent the heating wire from kinking or sideways

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Another feature of the is to avoid thermal expansion during its extension and thus to ensure that the contacts of the heating circuit are reliably opened Invention directed to the heating wire at its end forming a contact by a pretensioned spring to claim on train.

Another concern of the invention is to reduce the spark formation during regular opening and closing of the contacts of the device according to the invention, which operates in the manner of a two-point regulator. This purpose can only be achieved if the contacts are not gradual, i. H. proportional to the change in length of the Wire to move towards each other, but rather suddenly when the switching temperature is reached with each other Be brought into contact. This effect diminishes Another feature of the invention to achieve that the actuated by the free contact end of the Heizdrahteβ mating contact on a resilient and with certain Load automatically snapping membrane and at the contact end a membrane made of electrically non-conductive material existing, the mating contact with axial play (X) encompassing contact piece is attached. When the wire shrinks, the membrane is opened by the contact piece. H. withdrawn into their switching position at a certain cooling temperature. Due to the axial play between

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Switching element and mating contact can be easily adjusted, on the one hand, to determine the distance between the contacts when the heating circuit is interrupted, on the other hand set the switching hysteresis, d. H. that the switching points for switching the current on and off are not at the same temperature.

A simple adjustability of the snap position of the membrane and thus also the switching points of the contacts can be achieved according to a further proposal of the invention in that the mating contact is one in a threaded ring in the The center of the membrane is adjustably arranged screw and that the contact piece is behind the contact pill forming The head of the screw engages.

Of course, the spring stressing the heating wire in tension must be stronger than the spring force of the membrane, in order to be able to overcome the resistance of the membrane when the heating wire is elongated. In this regard, it is proposed in detail that that the spring stressing the heating wire on train is a compression spring which is on the one hand a Ceramic seat is supported on the closure piece, on the other hand on one end face of the contact piece.

The invention is now illustrated by means of exemplary embodiments in the drawing and in the description below these embodiments explained in more detail.

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It shows:

Fig. 1 in the form of a circuit diagram structure and

Mode of operation of the device according to the invention,

Fig. 2 each in charting the cooling curve, the results from the cooling of the cooled from 96O ⁰ C to 935.3 ° C of the heating wire, wherein the different converter temperatures,

3 also shows the charging and discharging behavior of the integrator capacitor in a diagram when switching the heating current on and off periodically,

4, in turn, as a diagram, the temperature profile in a catalytic converter, plotted over time, when simulating a spark plug defect,

Fig. 5 using a section through a catalytic converter, a possibility of constructive Realization of a temperature sensor according to the invention,

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6 shows, in an enlarged representation, a section along the line VI - VI in FIG. 5,

7 shows a section along the line VII - VII in FIG. 6,

8 shows a representation of the diaphragm visible in section from FIG. 6 in plan view and FIG

9 shows another embodiment of the invention Temperature sensor based on a section according to FIG. 5.

As indicated schematically in FIG. 1, there is a designated IO Temperature sensor for a catalytic converter as an exhaust gas decontamination system from a heating wire 11, the has a contact 12 at one end which cooperates with a mating contact 13. Heating wire 11 and contacts 12, 13 are components of a hot circuit that is operated by the Car battery 14 via a heating energy generator 15, for example a simple voltage divider or a voltage converter, is fed. If the temperature in the catalytic converter is high enough, the heating wire 11 elongates as a result its thermal expansion, and the power supply is interrupted. The heating wire 11 cools down according to the converter temperature quickly. It shortens itself again

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and switches on the electrical energy again at a certain temperature. So the way of working follows the principle of the two-position controller. Switching between an upper temperature and a lower temperature arises a clock frequency with the same switch-on duration and variable switch-off duration. An integrator 16 forms this Frequency into a variable DC voltage. A measuring instrument is connected to the output voltage of the integrator 16 17 connected. The DC voltage can, however, also be fed to a measuring trigger 18 in order to control an actuator 19 or turn on a warning lamp 20 at a certain temperature.

The time can respectively be read from the cooling curve in Fig. 2 required for the heating wire 11 in dependence on the respective converter temperature of 960 ⁰ C (the selected upper temperature at which the heating current is turned off) to 935.3 ° C ( selected lower temperature at which the heating current is switched on again). The corresponding times can also be read from the upper curve, which shows the idealized temperature profile in the heating wire, plotted against time. The dash-dotted line shows the heating with a higher heating current and a higher upper switching temperature.

To set the upper switching temperature (in this

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Example 96O ⁰ C) you only need to measure the first heating-up time with a cold converter until it is switched off for the first time with the heating current set. The length of the following heating times indicates the temperature hysteresis. The length of the heating-up time can be adjusted by the size of the heating power, while the switch-off time is adjusted to a lesser extent by shifting the upper switching temperature. The lower capacitor voltage curve (Fig. 3) shows that the measuring current depends only on the charging and discharging times.

From Fig. 4 it can be seen that with normal functionality of the spark plugs, the converter temperature is around 700 ° C, but that in the event of failure of a spark plug within only 40 seconds to the 960 ° C already mentioned above as the upper switching temperature and in the further course rises above 1000 ^{° C.} If such high temperatures are kept for a longer period of time, the converter mass would be destroyed. The measurement data which can be taken from FIG. 4 were determined on a vehicle with a four-cylinder engine in second gear at a speed of approx. 50 km / h.

FIG. 5 now shows one possibility of the structural design of the temperature sensor shown only schematically in FIG. 1 10. Here, 21 designates the housing and 22 the converter bed of a catalytic converter. The converter has a large opening 24 provided with a thread 23. The converter bed 22 with catalyst mass is fed through this opening 24

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25 filled. A hexagon 26 is used as a closure Closure piece 27, which with the temperature sensor 10 - as will be explained in more detail - forms a unit. Opposite to the opening 24 is a bearing on the converter wall 21

28 welded to which the bed 22 was also welded. The temperature sensor 10 is in a guide bore

29 stored so that it can move lengthways.

As can also be seen from FIG. 5 and partially also from FIG. B. 36 % Ni steel is stored. The heating wire 11 itself should have a high coefficient of thermal expansion and can accordingly, for. B. made of the material X 15Cr Ni Si 2520, a stainless steel. In the sleeve

30 individual ceramic bushings 31 are cemented in, in the central bores 32 of which the heating wire 11 is supported with play and is led. The heating wire 11 is attached to the end 33 of the sleeve 30.

As can be seen in particular from Fig. 6, the sleeve 30 is pressed at the other end into the closure piece 27 and with welded or cemented to this. The heating wire 11 is guided through a bore 34 in the closure piece 27. A Rivet 35 connects heating wire 11 to a contact piece

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A spring 37 tensions the heating wire 11 and presses the contact piece 36 against an adjusting contact screw 38, which is held by a switching membrane 39 against a contact at this point 40 forming rivet 35 is pressed in the contact piece 36. The resilient switching membrane 39 is designed so that they When pressed in, it first spreads and then snaps on from a certain position. The spreading is done by radial attached slots 46 allows (Fig. 8). The snap point can be changed by turning the adjusting contact screw 38 (slot 41) in a switching diaphragm threaded ring 42. The setting is secured with a lock nut 43.

The switching piece 36 is made of ceramic and - as FIG. 7 shows - is designed so that the head 44 of the adjusting screw 38 can be pushed into a longitudinal groove 45.

As can also be seen from FIG. 6, a play "X" is provided between the mating contact (screw head 44) and the contact piece 36. This defines the distance between the contacts 40 from one another in their open state. On the other hand, by the dimension "X" determines the hysteresis, the temperature difference that is, when turning on and off of the Heiζstromkreises (FIG. 2 935.3 ⁰ C and 960 ° C).

The switching membrane 39 is guided in an insulating ring 47 and on a contact ring 48 (with plug contact 49). The Burch

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knife enlargement of the switching membrane 39 during the spreading must be taken into account in the insulating ring 47. The plug contact 49 is inserted through a plastic cover 50. This is pressed into the closure piece 27 and seals it against dirt.

The closure piece 27 has - as already mentioned - one Hexagon 26 to screw the temperature sensor 10 tightly into the converter 21. A is used for better sealing Asbestos ring 51.

The embodiment of FIG. 8 differs from that of FIGS. 5 to 7 only in that the The sleeve surrounding the heating wire 11, denoted here by 30a, is not made of metal, but of ceramic material or glass. This material is particularly advantageous because of its low thermal expansion and conductivity. Also can Heating wire 11 here - in contrast to FIGS. 5 and 6 - are stored and required directly in the bore of the sleeve 30a no individual cemented guide bushes. In the embodiment according to FIG. 9, the sleeve 30a forms on the one end equal to the seat for the pretensioned spring 37, while in the embodiment of FIGS. 5 and 6 a separate one Spring seat 52 made of ceramic material is provided. Of the Heating wire 11 is passed through the sleeve 30a with some play and is soldered at the end to a metallic end cap 33a. The end cap 33a connects the heating wire 11 via the

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Guide bearing 28 with ground (negative pole of the battery).

The device described now works as follows. When the vehicle ignition is switched on, there is a plug contact 49 Voltage on. A current now flows through the contact ring 48, the switching membrane 39, the adjusting screw 38, the rivet 40, through the heating wire 11 to the end 33 or 33a of the sleeve 30 or 30a, which is connected to ground.

The heating wire 11 now elongates and the spring 37 moves the contact piece 36 against the diaphragm force. The membrane 39 spreads. When the switching temperature is reached, the membrane 39 quickly snaps on until the head 44 of the adjusting screw 38 is held by the contact piece 36. As a result, the current is interrupted and the heating wire 11 cools down. He pulls the contact piece 36 back. When the snap position is reached, the adjusting screw 38 opens again the contact 40 and the heating current flows again. This game is repeated until the engine is switched off. The switching membrane 39 has been chosen to reduce sparking. The point at which the membrane 39 snaps over, is set by means of the adjusting screw 38 and determines the upper temperature. Since the cooling time when the converter is cold is extremely short, the integrator 16 (Fig. 1) will give a high output voltage and thus the display instrument in contrast to when the system is switched off, make a full scale. Has the converter reached the lower switching temperature

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is enough, the instrument shows its smallest deflection. d. H. the lower switching point must be above the maximum permissible converter temperature.

So let a major advantage of the display device according to the invention that it shows its functionality by full blow when the ignition is switched on. Manufacturing tolerances can be adjusted by simply adjusting the Switching membrane 39 and the heating current can be compensated by measuring the heating times.

Claims

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Claims (1)

1. Device for protection against overheating or for displaying the temperature in exhaust gas decontamination systems, in particular catalytic converters or reactors, of Internal combustion engines, primarily in motor vehicles, characterized in that in the exhaust gas decontamination system (21, 22, 25) a constant current electrically heated wire (11) is arranged, the in the event of elongation as a result of heating by opening contacts (12, 13 or 40, 44), the heating circuit is automatically activated interrupts and closes it again automatically after cooling and that the temperature depends on the temperature in the exhaust gas decontamination system dependent cooling times of the heating wire as the starting point for the determination and display (17) of the temperature in the exhaust gas decontamination system and / or as a signal for switching on a warning display (20) and / or to switch off (19) the exhaust gas decontamination system. 2. Device according to claim 1, characterized in that the square curve of the heating system resulting from switching the circuit on and off Stromes (Fig.3) is fed to an integrator (16) for conversion and the uniform leaving the integrator Power to operate a temperature and / or warning display and / or an actuator (17 or 20 or 19) serves to switch off the exhaust gas decontamination system from the hot exhaust gas flow .. A09810 / 0538 3. Device according to claim 1 or 2 for a catalytic converter as an exhaust gas decontamination system, characterized in that the heating wire (11) is mounted and guided in a sleeve (30, 30a) which is surrounded at all times by the converter mass (25) (Fig. 5, 6 and 9). 4. Apparatus according to claim 3, characterized in that sleeve and heating wire length at least the entire width of the catalytic converter (21, 22). 5. Apparatus according to claim 3 or 4, characterized in that the heating wire (11) is fixed at one end to one end (33, 33a) of the sleeve (30, 30a) is connected and the other end of the heating wire protrudes from the associated open sleeve end and the one Forms contact (35, 40) for actuating the heating circuit. 6. Device according to one or more of claims 3 to 5, characterized in that the sleeve (30, 30a) is made of a material compared to the heating wire (11) low coefficient of thermal expansion. Λ 0 9 8 1 0/0538 7. Apparatus according to claim 6, characterized «that the sleeve (3Oa) consists of one ceramic material or glass (Fig. 9). 8 »Device according to claim 6, characterized in that the sleeve (30) consists of a Steel with about 36 tf nickel and the Heiedrftht (II) made of steel X 15Cr Nl Sl 2530 (Fig. 5 and 6). 9. Apparatus according to claim 8, characterized in that the heating wire (11) is guided at individual points within the sleeve (30) by means of cemented ceramic sleeves (31). 10. Device according to one or more of claims 3 to 9, characterized in that the housing (21) surrounding the converter has an opening (24) provided with a thread (23) which is closed by a closure piece (27) having a corresponding external thread. is lockable and that the closure piece inside is hollow and there the mating contact (38, 44) for the heating wire contact (35, 40) carries and that the end in question the sleeve (30, 30a) is firmly connected to the closure piece and the contact end (35, 40) of the heating wire (11) protrudes through a bore (34) into the interior of the closure piece (Fig. 6). 409810/0 5 38 11. The device according to claim 10, characterized in that the closure piece (27) remote closed end (33, 33a) of the sleeve (30, 30a) is held or guided in an axially movable manner in a bearing (28) connected to the converter housing (21) is. 12 · Device according to one or more of the claims 5 to 11, characterized in that the heating wire (11) is on its end forming a contact (35, 40) is subjected to tension by a pretensioned spring (37). 13. Device according to one or more of the claims 5 to 12, characterized in that the actuated by the free contact end (35, 40) of the heating wire (11) Mating contact (38, 44) on a resilient and automatically snapping on when a certain load occurs Membrane (39) and at the contact end (35, 40) made of electrically non-conductive material, the Mating contact under axial play (X) encompassing switching piece (36) is attached. 409810/0538 14. Apparatus according to claim 13, characterized in that the mating contact (38, 44) is one in a threaded ring (42) in the center of the membrane (39) is adjustably arranged screw and that the contact piece (36) behind the contact pill forming head (44) of the screw (38) engages. 15. Apparatus according to claim 13 or 14, characterized in that the spring (37) stressing the heating wire (11) in tension is a compression spring, on the one hand via a ceramic seat (52) on the closure piece (27), on the other hand on the one The face of the contact piece (36) is supported. 16. Device according to one or more of claims 13 to 15, characterized in that the resilient membrane (39) carrying the mating contact (38, 44) with its edge is fixed in the closure piece (27). 409 8 10/0538